High-sensitivity damage detection based on enhanced nonlinear dynamics**An earlier version was presented at the SPIE 11th International Symposium on SmartStructures and Materials.

Abstract

One of the most important aspects of detecting damage in the framework of structuralhealth monitoring is increasing the sensitivity of the monitored feature to the presence,location, and extent of damage. Distinct from previous techniques of obtaining informationabout the monitored structure—such as measuring frequency response functions—theapproach proposed herein is based on an active interrogation of the system. Thisinterrogation approach allows for the embedding of the monitored system within a largersystem by means of a nonlinear feedback excitation. The dynamics of the larger system isthen analyzed in state space, and the shape of the attractor of its dynamics is used as acomplex geometric feature which is very sensitive to damage. The proposed approach isimplemented for monitoring the structural integrity of a panel forced by transverse loadsand undergoing limit cycle oscillations and chaos. The nonlinear von Karmanplate theory is used to obtain a model for the panel combined with a nonlinearfeedback excitation. The presence of damage is modeled as loss of stiffness ofvarious levels in a portion of the plate at various locations. The sensitivity of theproposed approach to parametric changes is shown to be an effective tool in detectingdamages.